Sorbent compositions for the removal of boron from aqueous mediums

ABSTRACT

Sorbent compositions that include a base sorbent material having a high porosity and surface area and a boron-selective agent are particularly useful for the sequestration of boron from waste materials such as coal combustion residual leachate (CCRs). By using a boron-selective agent in conjunction with a high surface area base sorbent material such as activated carbon or biochar, a sorbent composition with a high capacity for sequestering boron at relatively low cost is provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. Provisional PatentApplication No. 62/434,901 filed on Dec. 15, 2016, entitled “SORBENTCOMPOSITIONS FOR THE REMOVAL OF BORON FROM AQUEOUS MEDIUMS,” which isincorporated herein by reference in its entirety.

FIELD

This disclosure relates to the treatment of aqueous mediums (e.g., wastewater, ground water, etc.) to remove boron and/or borates, and relatesto sorbent compositions that are useful for such treatment, and tomethods for making such sorbent compositions.

BACKGROUND

Regulations for groundwater monitoring and corrective action of coalcombustion residuals (CCR, primarily composed of coal ash) landfills andsurface impoundments were put in place by the Coal Combustion ResidualsRule (40 CFR Parts 257 and 261) calling for viable remedy options to bemade available. Among the elements subject to regulation is boron, whichis known to be harmful to animals and humans in elevated concentrations,and may cause gastrointestinal disorders, central nervous systemdisorders, and the like. Leachate from CCRs commonly include a boronconcentration of about 1 ppm to 14 ppm.

The World Health Organization (WHO) limit for boron in drinking water is2.4 mg/L, and several states have limits ranging from 0.6 mg/L to 1mg/L. Boron has a high potential for contaminating groundwater at CCRsites because it is the most abundant of the minor elements found incoal ash, is highly mobile in an aqueous environment, and doesn'treadily precipitate. It is not typically removed by conventional watertreatment methods, and removal requires high-cost methods such as boronspecific ion exchange resins, reverse osmosis, and/orelectro-deionization. Interest has been focused on the possibility ofin-situ, passive treatment, such as permeable reactive barriers, forremediation at CCR landfills and surface impoundments.

A boron specific ion exchange resin is the most widely used selectiveboron removal technology, but it is limited by the resin'shydrophobicity, moderate surface area, large chemical requirements forregeneration, and high price.

SUMMARY

Existing removal technologies are not readily adaptable for in-situtreatment to remove boron from aqueous mediums, and a need for a longlasting, high capacity, boron sorbent has been recognized. Otherindustries that also require selective removal of boron from aqueousmediums may also benefit from the sorbents and methods disclosed herein.These include, but are not limited to, flue gas desulfurization wastewater, produced water, desalinization, ultra-pure water, agriculturalwater, geothermal water, and landfill leachate.

The present disclosure provides a sorbent composition having a favorablecapacity for removal of boron and/or borates from an aqueous solution.The sorbent composition includes a base sorbent material having a highsurface area, such as activated carbon or biochar. A boron-selectiveagent is combined with (e.g., deposited on) the base sorbent material.By using a boron-selective agent in conjunction with a high surface areabase sorbent material such as activated carbon or biochar, a sorbentcomposition with a high capacity for sequestering boron and a relativelylow cost is provided.

In one embodiment, a sorbent composition is disclosed. The sorbentcomposition includes a base sorbent material and a boron-selective agentthat is combined with the base sorbent material. The boron-selectiveagent is selected to increase the removal of boron from an aqueousmedium as compared to the untreated base sorbent material, e.g., ascompared to the base sorbent material that has not been combined withthe boron-selective agent. By way of example, the base sorbent materialmay be a high surface area material such as activated carbon, e.g.,powdered activated carbon or granulated activated carbon, or biochar.The boron-selective agent may be selected from several compounds (e.g.,classes of compounds) that are selected to enhance the sequestration ofboron by the base sorbent material, such as by forming stable molecularcomplexes with the boron.

In another embodiment, a method for the manufacture of a sorbentcomposition is disclosed, where the method includes contacting a basesorbent material with a boron-selective agent, where the boron-selectiveagent enhances the removal of boron from an aqueous medium as comparedto the untreated base sorbent material. For example, the combining stepmay include contacting the base sorbent material with a solutioncomprising the boron-selective agent. In other characterization, thecombining step may include admixing particulates of the base sorbentmaterial with particulates of the boron-selective agent.

In another embodiment, a method for reducing the boron concentration inan aqueous medium is disclosed. The method may include contacting anaqueous medium with a base sorbent material in the presence of aboron-selective agent. The boron-selective agent may be combined withthe base sorbent material, e.g., before being contacted with the aqueousmedium. Alternatively, the boron-selective agent may be dispersed intothe aqueous medium before or during contact of the aqueous medium withthe base sorbent material.

These and other embodiments and characterizations of a sorbentcomposition, a method for manufacturing a sorbent composition and amethod for using the sorbent composition will become apparent from thefollowing description.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure is directed to sorbent compositions, methods formaking the sorbent compositions and methods for using the sorbentcompositions, e.g., to selectively remove boron species from an aqueousmedium such as wastewater. The sorbent compositions are capable ofremoving boron species from aqueous mediums and also have a highcapacity for boron sequestration (e.g., for boron removal). The sorbentcompositions may also be relatively cost-effective as compared to knownmethods for the removal of boron from aqueous mediums. The boron speciessequestered by the sorbent compositions disclosed herein may includeelemental boron or borates, for example. Although the followingdescription refers to the removal of boron and the use of a boronselective agent for the sake of convenience, the boron selective agentencompasses those agents that are useful for the sequestration of bothelemental boron and/or boron compounds, e.g. ionic compounds such asborates.

Broadly characterized, the sorbent compositions include a combination ofa base material (e.g., a base sorbent material) having a relatively highporosity and a high surface area, and a boron-selective agent.

The base sorbent material may advantageously have a high pore volume. Inone characterization, the base sorbent material has a total pore volume(sum of micropore volume plus mesopore volume plus macropore volume) ofat least about 0.10 cc/g, such as at least 0.20 cc/g, at least about0.25 cc/g or even at least about 0.30 cc/g. In certaincharacterizations, the micropore volume of the base sorbent material maybe at least about 0.10 cc/g, such as at least about 0.15 cc/g. Further,the mesopore volume (i.e., pores having a diameter of from 20 Å to 500Å) may be at least about 0.10 cc/g, such as at least about 0.15 cc/g. Inone characterization, the ratio of micropore volume (i.e., pores havinga diameter of not greater than 20 Å) to mesopore volume in the basesorbent material may be at least about 0.7, such as 0.9, and may be notgreater than about 1.5. Such levels of micropore volume relative tomesopore volume may advantageously enable efficient capture andsequestration of boron species (e.g., boron and/or borates) by the basesorbent material. Pore volumes may be measured using gas adsorptiontechniques (e.g., N₂ adsorption) using instruments such as a TriStar IISurface Area Analyzer 3020 or ASAP 2020 (Micromeritics InstrumentsCorporation, Norcross, Ga., USA).

In another characterization, the base sorbent material has a relativelyhigh surface area. In one characterization, the base sorbent materialmay have a surface area of at least about 25 m²/g, such as at leastabout 50 m²/g, and up to about 125 m²/g, such as up to about 100 m²/g.Surface areas in this range may be provided by base sorbent materialssuch as biochar. For other applications, higher surface area basesorbent materials may be more effective. In one such characterization,the base sorbent material may have a surface area of at least about 350m²/g, such as at least about 400 m²/g, at least about 500 m²/g, at leastabout 600 m²/g, or even at least about 1000 m²/g. Such high surfaceareas may be provided by activated carbons, for example. Surface areamay be calculated using the Brunauer-Emmett-Teller (BET) theory orDensity Functional Theory (DFT) equation that models the physicaladsorption of a monolayer of nitrogen gas molecules on a solid surfaceand serves as the basis for an analysis technique for the measurement ofthe specific surface area of a material. BET surface area may bemeasured using the Micromeritics TriStar II 3020 or ASAP 2020(Micromeritics Instrument Corporation, Norcross, Ga.).

Useful base sorbent materials may advantageously comprise particles(e.g., free flowing particles) that are highly porous and have a highsurface area. For example, the base sorbent material may comprise porouscarbonaceous particles, zeolite particles, silica particles (includingsilica gel), alumina particles (e.g., activated alumina), clay particles(e.g., aluminosilicates) and combinations thereof. In one embodiment,the base sorbent material includes porous carbonaceous particles.Examples of porous carbonaceous particles include activated carbon suchas powdered activated carbon (PAC) and/or granular activated carbon(GAC), reactivated carbon, carbonaceous char such as biochar (e.g., aporous material made from biomass by pyrolysis), and combinationsthereof. In one particular characterization, the base sorbent materialincludes activated carbon and/or biochar. In this regard, although thefollowing discussion primarily refers to the use of porous carbonaceousparticles as the base sorbent material, specifically activated carbon,the sorbent compositions of the present disclosure are not so limited.The activated carbon may be derived from a variety of sources (e.g.,feedstocks), including anthracite coal, bituminous coal, lignite coal,coconut shells, wood, and the like. In one characterization, theactivated carbon is derived from a lignite coal feedstock, whichgenerally has a higher mineral ash content than activated carbon derivedfrom anthracite coal.

In certain embodiments, the base sorbent material comprises particleshaving a relatively small median average particle size (D50), e.g., toenhance the efficiency of boron sequestration by the sorbentcomposition. In one characterization, the median average particle sizeof the base sorbent material is not greater than about 100 μm, such asnot greater than 75 μm, not greater than 50 μm, such as not greater thanabout 30 μm, or even not greater than about 25 μm. In some applications,it may be desirable to utilize a base sorbent material having a medianaverage particle size of not greater than about 20 μm, not greater thanabout 15 μm and even not greater than about 12 μm. Characterized inanother way, the median (D50) particle size of the base sorbent materialmay be at least about 5 μm, such as at least about 6 μm, or even atleast about 8 μm. On example of such a base sorbent material is PAC. TheD50 median average particle size may be measured using techniques suchas light scattering techniques (e.g., using a Saturn DigiSizer II,available from Micromeritics Instrument Corporation, Norcross, Ga.).

Depending upon the application of the sorbent composition, it may bedesirable to utilize base sorbent materials having a larger averagesize, e.g., in the form of agglomerates or aggregates, e.g., granules.For example, the base sorbent material may be in the form of granuleshaving a median size of at least about 0.2 mm, such as at least about0.3 mm. Typically, the granules will have a median size of not greaterthan about 3.0 mm, such as not greater than about 2.5 mm. In anothercharacterization, the granules may have a mesh size of about 8×20, about8×30, or about 20×40 in the Tyler mesh series. In one characterization,the granules comprise activated carbon, i.e., granulated activatedcarbon (“GAC”).

In another example, the base sorbent material may be in the form ofextrudates, e.g., pellets that are formed by extrusion or a similarprocess. For example, the base sorbent material may be in the form ofextruded pellets of activated carbon and/or of biochar.

Although free-flowing particles, granules or extrudates of the basesorbent material are described above, the use of larger, rigid orsemi-rigid porous bodies (e.g., porous honeycomb structures) that arecombined with the boron-selective agent are also contemplated by thepresent disclosure.

According to an embodiment of the present disclosure, the base sorbentmaterial is combined with a boron-selective agent to form the sorbentcomposition. There are a wide variety of compounds that are capable ofenhancing the boron sequestration of the base sorbent material, e.g. byboron complexation. In one characterization, the boron selective agentcomprises a compound that includes a 1,2 hydroxyl, 1,2 carboxyl or 1,2carbonyl group. Particular examples of such compounds include, but arenot limited to, sorbitol, mannitol, polyvinyl alcohol (PVA), 1,2ethanediol, 1,2 propanediol, catechol, cyclodextrin, tannic acid,glucose, mannose, glycerol, ribose, cellulose, curcumin, citric acid,tartaric acid and malic acid.

The boron-selective agent may also be selected from compounds thatinclude 1,3 hydroxyl, 1,3 carboxyl or 1,3 carbonyl groups. Examples ofsuch compounds include, but are not limited to, salicyl alcohol, 1,3propanediol, bis(hydroxymethyl)phenol, salicylic acid and dihydroxylbenzonic acid.

The boron-selective agents listed above may also include amino or iminogroups. Examples include, but are not limited to, imino bis propyleneglycol, n-methyl-glucamine, and octyl-glucamine.

In an aqueous environment, boron is present as a weak Lewis Acid, namelyboric acid (B(OH)₃), and accepts a hydroxyl ion to form the borate anion(pKa=9.24). While not wishing to be bound by any particular theory, itis believed that boric acid and borate ions form stable complexes insolution with 1,2 or 1,3 hydroxyl (carbonyl or carboxyl) groups that arein the favorable cis conformation for boron coordination. Either neutralboron esters or borate complex anions with a proton as a counter ion areformed. Compounds such as organic acids, alcohols and polyols includethis favorable orientation of hydroxyl groups. The addition of an iminoor amino group to the polyol, as noted above, may neutralize the protonrejected during borate complex formation. Thus, these compounds orderivatives of these compounds may be used as the boron selective agentwith the base sorbent material to form a boron-specific sorbentcomposition.

The removal of boron and/or borates from an aqueous medium may also befacilitated by the use of divalent or trivalent ions present on the basesorbent surface or in the waste stream. Examples include, but are notlimited to, Ca²⁺, Cu²⁺, Zn²⁺, Fe²⁺, Fe³⁺, and Al³⁺. For example, saltsthat are soluble in the waste stream (e.g., chloride salts) may becombined with the sorbent composition, and/or may be added to the wastestream to provide the ions in solution. Such cations may react with theboron species in or on the pores of the base sorbent material. Thesorbent composition may be formed such that the salt forms animmobilized cation on the sorbent surface (e.g., on the carbon surface)that may form a complex with the boron in the form of a precipitate thatmay be separated from the aqueous medium.

The removal of boron and borates may also be facilitated by the use ofsurfactants as the boron-selective agent, either alone or in combinationwith one or more of the compounds described above. Useful surfactantsmay include those with charge classification as anionic, cationic,nonionic or amphoteric. By way of example, cationic salts may enable iondisplacement of the cation of the surfactant and reaction with the boronspecies to form a new compound that can be removed from the liquidstream. Examples of such cationic salts include, but are not limited to,quaternary ammonium salts such as quaternary ammonium chlorides,quaternary ammonium bromides and quaternary ammonium methyl sulfates.Additionally, amphoteric salts may be useful to change the ioncharacteristics based on the pH and ions present in a solution, thusallowing reaction with the boron species to form a new compound that canbe removed. Examples of such amphoteric salts include, but are notlimited to, those containing nitrogen such as alkyl amidopropylbetaines, alky ampho acetates and alky ampho propionates. Further,cationic and amphoteric surfactants may also function as a flocculentthat increase the molecular weight of the boron species being removed.Anionic and nonionic surfactants can also enable the dispersion ofborates to facilitate transfer into the porous regions of the sorbentmaterial.

The sorbent composition comprises an effective amount of one or more ofthe boron-selective agent(s) to effectuate the removal of boron and/orborates from a fluid such as an aqueous (water-based) medium. In onecharacterization, the sorbent composition comprises at least about 0.1wt. % of a boron-selective agent, such as at least about 1 wt. % of aboron-selective agent, such as at least about 3 wt. % of aboron-selective agent, or at least about 5 wt. % of a boron-selectiveagent. However, too high of a concentration of the boron-selective agentmay not increase the capacity or efficiency of boron sequestration, andmay even be detrimental. In once characterization, the concentration ofa boron-selective agent in the sorbent composition is not greater thanabout 50 wt. %, such as not greater than about 30 wt. %, such as notgreater than about 20 wt. %, or even not greater than about 10 wt. %.

Various techniques may be used to combine the base sorbent material withthe boron-selective agent. For example, the boron-selective agent willtypically be in the form of a solution and/or slurry, such as bydissolving the boron-selective agent in water. The solution and/orslurry may then be brought into contact with the base sorbent materialto coat and/or impregnate the base sorbent material with the solutionand/or slurry. One such technique is the incipient wetness technique,wherein the solution is drawn into the pores of the base sorbentmaterial via capillary action. Other techniques include spraying theboron-selective agent solution and/or slurry onto the base sorbentmaterial, impregnating the base sorbent material by soaking it in thesolution and/or slurry followed by washing steps, reacting theboron-selective agent to the surface of the base sorbent material, orimmobilizing the boron-selective agent on the base sorbent material'ssurface. Another technique involves injecting the boron-selective agentinto the liquid, where it would form complexes with the boron insolution to subsequently be absorbed by the base sorbent material. Inany case, the solution may be dried, if necessary, to remove excessliquid and/or to crystallize the boron-selective agent.

In an alternative embodiment, the boron-selective agent may be providedin a substantially dry form (e.g., as particulates) and may be admixedwith the base sorbent material, such as by combining the two particularcomponents in a mill or in a mixing unit.

In one embodiment, the base sorbent material may be treated before(pretreated) or after being combined with the boron-selective agent. Forexample, the base sorbent material may be pretreated by contacting thebase sorbent material with a base or an acid (e.g., HNO₃). A base mayfacilitate the attachment of the boron-selective agent (e.g., tartaricacid) to the base sorbent material. In another example, the base sorbentmaterial may be treated by ozonating the surface of the base sorbentmaterial, i.e., by contacting the base sorbent material with aneffective amount of ozone. Ozone treatment may advantageously placeoxygen groups on the base sorbent material surface (e.g., carbonsurface) that have an affinity for the boron species, e.g., for boricacid.

Another embodiment of the present disclosure is directed to methods forthe removal and/or sequestration of boron (e.g, boron or other boronspecies such as borates), particularly for the removal of boron fromaqueous (water-based) mediums. Such aqueous mediums may include, but arenot limited to, waste streams from CCR landfills, metal fabrication andprocessing (e.g., electroplating), electrical component manufacture, andthe like. Other aqueous streams that include elevated levels of boroninclude the desalinated water from desalinization plants utilizingreverse osmosis and geothermal water.

To facilitate the removal of boron from an aqueous medium, the methodincludes contacting the aqueous medium with a base sorbent material inthe presence of a boron-selective agent. The boron-selective agent maybe combined with the base sorbent material, e.g., before being contactedwith the aqueous medium, as is discussed above. Alternatively, theboron-selective agent may be dispersed into the aqueous medium before orduring contact of the aqueous medium with the base sorbent material,e.g, with a base sorbent material that has not been combined with theboron-selective agent.

As is known to those of skill in the art, the sorbent compositionsincluding the base sorbent and the boron-selective agent may becontacted with the aqueous medium (e.g., waste stream) to remove boronin a wide variety of ways. For example, the sorbent composition may beplaced in a cartridge or similar structure through which the aqueousmedium flows. In another example, the sorbent composition may be placedon or within a membrane (e.g., a planar membrane) through which theaqueous medium flows. The sorbent composition may also be shaped into anintegral structure (e.g., a honeycomb structure, porous carbon blocks)or may be incorporated into such a structure (e.g., a ceramic honeycombstructure). The sorbent composition may also be used in a permeablereactive barrier, such as where the sorbent composition is either buriedin a trench or is injected into the subsurface to treat contaminatedgroundwater.

In certain characterizations, the sorbent compositions disclosed hereinhave a relatively high capacity for boron removal. In one embodiment,the sorbent compositions have a capacity to capture at least about 1 mgboron per gram of sorbent composition (mg B/g), such as at least about 2mg B/g, at least about 5 mg B/g, at least about 7.5 mg B/g, at leastabout 10 mg B/g, at least about 15 mg B/g, or even at least about 20 mgB/g.

In a further characterization, the sorbent composition mayadvantageously capture (e.g., sequester) the boron in the presence ofother contaminants. Merely by way of example, the sorbent compositionmay be useful for the treatment of CCRs including other contaminantssuch as those listed in Table I below:

TABLE I CCR Constituents Starting Leachate Target ContaminantContaminant Level [mg/L] Level [mg/L] MCL 90th (health based) orConstituent Median Percentile Maximum SMCL/State limit Boron 2.6 14 1120.6-1   Calcium Chloride 28 74 2330 200-250 Fluoride 0.163 1.312 8.85 4Sulfate 485 1613 30500 250-400 Total Dissolved 500 Solids pH (field)Antimony 0.002 0.02 0.59 0.006 Arsenic 0.026 0.178 1.38 0.01 Barium0.089 0.25 0.657 2 Beryllium BDL BDL 0.009 0.004 Cadmium 0.002 0.0130.065 0.005 Chromium 0.001 0.025 5.1 0.1 Cobalt Lead BDL 0.0004 0.0080.015 Lithium 0.15 0.43 23.6 0.17 Mercury 4E−06 0.000029 0.000079 0.002Molybdenum 0.36 1.39 60.8 0.35-0.73 Selenium 0.018 0.181 2.36 0.05Thallium BDL 0.005 0.018 0.002 Fluoride 0.163 (lab) 1.312 (lab) 8.85(lab) 4 Radium 226 & 228 5 pCi/L

The sorbent compositions of the present disclosure may be formulated toremove boron even when the boron is present with such othercontaminants, such as in a CCR waste stream. In anothercharacterization, the sorbent composition may be formulated to enableone or more of the other contaminant elements to be captured with theboron. For example, the sorbent composition may be formulated to alsoremove elements such as selenium and/or arsenic from the aqueous medium,along with the boron species.

EXAMPLES Example 1

Comparative Sample A is comprised of a granular activated carbon (GAC)derived from bituminous coal feedstock. The GAC is characterized ashaving a mesh size of 8×30, a surface area of at least about 350 m²/g,and a total pore volume of at least about 0.3 cc/g. A batch test is usedto evaluate the ability of the sorbent to remove boron from an aqueoussolution. Carbon is dosed into a standard solution containing 10 ppmboron, and the mixture is stirred for about 24 hours at roomtemperature. The solution is then vacuum filtered and analyzed for totalboron content via inductively coupled plasma (ICP). The result,expressed as percent boron removed from solution, is expressed in TableII.

Example 2

Comparative Sample B is made by grinding Comparative Sample A down to apowder using a lab-scale disk mill followed by a lab-scale jet mill.Comparative Sample B is characterized as having a median particle size(D50) of about 12 μm. The ability to remove boron is assessed using abatch test and the result is expressed in Table II as percent boronremoved from solution.

Example 3

To test for enhanced boron removal, Sample C is formed by adding a diolfunctionality (N-Methyl-D-Glucamine) to comparative Sample B. The firststep in preparation is to dissolve 3.4 g of N-Methyl-D-Glucamine in 5.1g of deionized water. 4.25 g of this solution is sprayed onto 8.3 g ofSample B while fluidizing the PAC in a mixer for 10 minutes to yieldSample C containing about 17 wt. % N-Methyl-D-Glucamine. The ability toremove boron is assessed using a batch test and the result is expressedin Table II as percent boron removed from solution.

Example 4

To test for enhanced boron removal, Sample D is formed by adding a diolfunctionality (N-Methyl-D-Glucamine) to comparative Sample B. Forpreparation, 1.7 g of N-Methyl-D-Glucamine and 8.3 g of Sample B aremixed in a fluidizing mixer for 10 minutes to yield Sample D whichcontains about 17 wt. % N-Methyl-D-Glucamine. The ability to removeboron is assessed using a batch test and the result is expressed inTable II as percent boron removed from solution.

Example 5

To test for enhanced boron removal, Sample E is formed by adding a diolfunctionality (sorbitol) to comparative Sample B. The first step inpreparation is to dissolve 3.4 g of sorbitol in 5.1 g of deionizedwater. 4.25 g of this solution is sprayed onto 8.3 g of Sample B whilefluidizing the PAC in a mixer for 10 minutes to yield Sample E whichcontains about 17 wt. % sorbitol. The ability to remove boron isassessed using a batch test and the result is expressed in Table II aspercent boron removed from solution.

Example 7

To test for enhanced boron removal, Sample F is formed by adding a diolfunctionality (sorbitol) to comparative Sample B. For preparation, 1.7 gof sorbitol and 8.3 g of sample B are mixed in a fluidizing mixer for 10minutes to yield Sample F which contains about 17 wt. % sorbitol. Theability to remove boron is assessed using a batch test and the result isexpressed in Table II as percent boron removed from solution.

Example 8

To test for enhanced boron removal, Sample G is formed by adding a diolfunctionality (sorbitol) to comparative Sample A. For preparation, 1.7 gof sorbitol and 8.3 g of Sample A are mixed in a fluidizing mixer for 10minutes to yield Sample G which contains about 17 wt. % sorbitol. Theability to remove boron is assessed using a batch test and the result isexpressed in Table II as percent boron removed from solution.

TABLE II Results for Boron Removal Base Boron Sorbent AdditiveApplication Dosage Removal Sample Material (wt. %) Additive Method (wt.%) (%) A* GAC 0 — — 0.5 28 B* PAC 0 — — 0.5 34 C PAC 17 Methyl Solution0.5 49 Glucamine D PAC 17 Methyl Dry add mix 0.6 60 Glucamine E PAC 17Sorbitol Solution 0.5 62 F PAC 17 Sorbitol Dry add mix 0.6 76 G GAC 17Sorbitol Dry add mix 0.6 70 *comparative sample

While various embodiments of a sorbent composition, a method for themanufacture of a sorbent composition and a method for removing boronfrom an aqueous medium have been described in detail, it is apparentthat modifications and adaptations of those embodiments will occur tothose skilled in the art. However, it is to be expressly understood thatsuch modifications and adaptations are within the spirit and scope ofthe present disclosure.

What is claimed is:
 1. A sorbent composition comprising a base sorbentmaterial selected from the group consisting essentially of activatedcarbon, biochar, alumina, silica, clays, zeolites, and combinationsthereof and a boron-selective agent that is combined with the basesorbent material, wherein the boron-selective agent increases removal ofboron from an aqueous medium as compared to an untreated base sorbentmaterial, wherein the boron-selective agent comprises a compoundselected from the group of compounds comprising 1,2 hydroxyl groups, 1,2carboxyl groups, 1,2 carbonyl groups, 1,3 hydroxyl groups, 1,3 carboxylgroups, 1,3 carbonyl groups, and combinations thereof.
 2. The sorbentcomposition recited in claim 1, wherein the base sorbent material has atotal pore volume of at least about 0.10 cc/g.
 3. The sorbentcomposition recited in claim 1, wherein the base sorbent material has asurface area of at least about 50 m²/g.
 4. The sorbent compositionrecited in claim 1, wherein the base sorbent material comprisesactivated carbon.
 5. The sorbent composition recited in claim 1, whereinthe base sorbent material comprises biochar.
 6. The sorbent compositionrecited in claim 1, wherein the boron-selective agent comprises acompound selected from the group of compounds comprising 1,2 hydroxylgroups, 1,2 carboxyl groups, 1,2 carbonyl groups, and combinationsthereof.
 7. The sorbent composition recited in claim 6, wherein theboron-selective agent comprises a compound selected from the groupconsisting of sorbitol, mannitol, polyvinyl alcohol (PVA), 1,2ethanediol, 1,2 propanediol, catechol, tannic acid, glucose, mannose,glycerol, ribose, cellulose, curcumin, citric acid, tartaric acid, malicacid, and combinations thereof.
 8. The sorbent composition recited inclaim 1, wherein the boron-selective agent comprises a compound selectedfrom the group consisting of compounds comprising 1,3 hydroxyl groups,1,3 carboxyl groups, 1,3 carbonyl groups, and combinations thereof. 9.The sorbent composition recited in claim 8, wherein the boron-selectiveagent comprises a compound selected from the group consisting of salicylalcohol, 1,3 propanediol, bis(hydroxymethyl)phenol, salicylic acid,dihydroxyl benzonic acid, and combinations thereof.
 10. The sorbentcomposition recited in claim 1, wherein the boron-selective agentcomprises a functional group that is selected to neutralize a displacedhydrogen atom during boron complexation.
 11. The sorbent compositionrecited in claim 10, wherein the functional group is selected from thegroup consisting of an imino group, an amino group, and combinationsthereof.
 12. The sorbent composition recited in claim 11, wherein theboron-selective agent comprises a compound selected from the groupconsisting of imino bis propylene glycol, methyl-glucamine,octyl-glucamine, and combinations thereof.
 13. The sorbent compositionrecited in claim 1, wherein the boron-selective agent comprises adivalent or trivalent cationic salt, wherein the cation in the divalentor trivalent cationic salt is selected from the group consisting ofCa²⁺, Cu²⁺, Zn²⁺, Fe²⁺, Fe³⁺, Al³⁺, and combinations thereof.
 14. Thesorbent composition recited in claim 1, wherein the boron-selectiveagent comprises a surfactant.
 15. A sorbent composition comprising: abase sorbent material selected from the group consisting of activatedcarbon, biochar, and combinations thereof; and a boron-selective agentthat is combined with the base sorbent material, wherein theboron-selective agent comprises a compound selected from the group ofcompounds comprising 1,2 hydroxyl groups, 1,2 carboxyl groups, 1,2carbonyl groups, 1,3 hydroxyl groups, 1,3 carboxyl groups, 1,3 carbonylgroups, and combinations thereof.
 16. The sorbent composition recited inclaim 15, wherein the base sorbent material has a total pore volume ofat least about 0.10 cc/g and a surface area of at least about 50 m²/g.17. A sorbent composition comprising: a base sorbent material selectedfrom the group consisting of activated carbon, biochar, and combinationsthereof and having a total pore volume of at least about 0.10 cc/g, aratio of micropore volume to mesopore volume of at least about 0.7 andnot greater than about 1.5, and a surface area of at least about 50m²/g; and a boron-selective agent that is combined with the base sorbentmaterial, wherein the boron-selective agent is present in an amount ofat least about 0.1 wt. % to less than about 50 wt. % of the sorbentcomposition and comprises a compound selected from the group ofcompounds comprising 1,2 hydroxyl groups, 1,2 carboxyl groups, 1,2carbonyl groups, 1,3 hydroxyl groups, 1,3 carboxyl groups, 1,3 carbonylgroups, and combinations thereof, wherein the boron-selective agentincreases removal of one or more of elemental boron, a borate, and boricacid from an aqueous medium as compared to an untreated base sorbentmaterial lacking the boron-selective agent.
 18. The sorbent compositionrecited in claim 1, wherein the boron-selective agent is present in anamount of at least about 0.1 wt. % and less than about 50 wt. % of thesorbent composition.
 19. The sorbent composition recited in claim 1,wherein the boron-selective agent is present in an amount of at leastabout 1 wt. % of the sorbent composition.
 20. The sorbent compositionrecited in claim 1, wherein the boron-selective agent is present in anamount of less than 30 wt. % of the sorbent composition.
 21. The sorbentcomposition recited in claim 1, wherein the base sorbent material has amedium average particle size (D₅₀) of less than about 100 μm.
 22. Thesorbent composition recited in claim 1, wherein the base sorbentmaterial has a medium average particle size (D₅₀) of less than about 25μm.
 23. The sorbent composition recited in claim 1, wherein the basesorbent material has a ratio of micropore volume to mesopore volume ofat least about 0.7 and not greater than about 1.5.
 24. The sorbentcomposition recited in claim 1, wherein the base sorbent material is ina form of a granule having a median size of at least about 0.2 mm andless than about 3.0 mm.
 25. The sorbent composition recited in claim 1,wherein the boron is one or more of elemental boron, a borate, and boricacid.
 26. The sorbent composition recited in claim 1, wherein thesorbent composition has a capacity to capture at least 1 mg boron pergram of the sorbent composition.
 27. The sorbent composition recited inclaim 1, wherein the sorbent composition has a capacity to capture atleast 20 mg boron per gram of the sorbent composition.
 28. The sorbentcomposition recited in claim 15, wherein the boron-selective agentcomprises a compound selected from the group consisting of sorbitol,mannitol, polyvinyl alcohol (PVA), 1,2 ethanediol, 1,2 propanediol,catechol, tannic acid, glucose, mannose, glycerol, ribose, cellulose,curcumin, citric acid, tartaric acid, malic acid, salicyl alcohol, 1,3propanediol, bis(hydroxymethyl)phenol, salicylic acid, dihydroxylbenzonic acid, sorbitol, and combinations thereof.
 29. The sorbentcomposition recited in claim 17, wherein the boron-selective agentcomprises a compound selected from the group consisting of sorbitol,mannitol, polyvinyl alcohol (PVA), 1,2 ethanediol, 1,2 propanediol,catechol, tannic acid, glucose, mannose, glycerol, ribose, cellulose,curcumin, citric acid, tartaric acid, malic acid, salicyl alcohol, 1,3propanediol, bis(hydroxymethyl)phenol, salicylic acid, dihydroxylbenzonic acid, sorbitol, and combinations thereof.